What year was the combined attack on Libyan terrorist support bases carried out?

The correct year for the combined attack on Libyan terrorist support bases is 1986. This operation, known as "Operation El Dorado Canyon," involved U.S. airstrikes targeting several locations in Libya, including the capital city of Tripoli and the city of Benghazi. The strikes were a response to Libyan involvement in terrorism, particularly in connection to the bombing of a discotheque in West Berlin that killed several American servicemen and injured many others. The operation aimed to deter future Libyan-sponsored terrorism and demonstrate U.S. resolve against such acts.

Context about the other years indicates that 1985 and 1987 are not associated with this specific combined attack, while 1984 predates the more widely recognized involvement of U.S. military action against Libya during this conflict period. Therefore, 1986 is established as the significant year when military action was taken, making it the correct answer.